1. Field of the Invention
The present invention relates to an automobile engine starter for preventing an automobile engine from being started by a wrong key.
2. Related Art
An automobile engine starter of the sort stated above is designed to check a key inserted into an ignition key cylinder to see if it is a right key so as to justify the attempt to start the engine when it is the right one or vitiate the attempt when it is a wrong one, and further to perform the operation of informing those around an automobile of an unlawful act being committed by issuing warning, for example.
In order to decide whether the key inserted in the ignition key cylinder is right or wrong in that case, there is a known arrangement in which the key plate of a key is furnished with a resistor having a specific resistance, whereas an ignition key cylinder is fitted with a detector or the like for reading the resistance of the resistor provided therein when the key is inserted.
Another arrangement that has been proposed is to provide a resonance circuit having a specific frequency in the key grip of a key so that resonance may occur at the specific frequency, and a detecting device for reading the resonance frequency of the resonance circuit of the key.
A resistance and a resonance frequency are respectively set in the resistor and the resonance circuit on the key side as a physical quantity proper to an automobile, whereas the device for detecting the physical quantity is installed on the ignition key cylinder side in the manner mentioned above, whereby the key in question is decided to be a right one by detecting and verifying the physical quantity proper to the automobile.
However, the aforementioned conventional arrangements have been found unacceptable in respect to the following points:
In the case where the resistor is planted in the key plate, there are only about 20 kinds of resistors at the most in which any identifiable resistances in the range of given resistances fit for detection may be set. In order to detect the resistance of such a resistor, it is necessary to provide a key plate with a contact which is allowed to electrically make contact with the ignition key cylinder side. The problem in this case is that periodic maintenance is required to deal with, for example, the frictional wear and contact failure of the contact.
In the case where, with the resonance circuit provided for the key grip, its resonance frequency is detected on the ignition key cylinder side, only several tens of frequencies at the most may be put to practical use as identifiable frequencies in the range of given frequencies.
In other words, the total number of physical quantities that can be set is restricted in the conventional arrangements above in which, by setting a discrete physical quantity such as the resistance, the resonance frequency or the like on the key side, the physical quantity is examined and verified on the ignition key cylinder side. It is therefore hardly possible to improve security. If it is conversely attempted to improve security, there will arise the necessity of setting a highly-precise physical quantity and a device for detecting it. This is also disadvantageous in that additional cost may be incurred.